Some electorates - including most Māori electorates - have considerable influence on which MPs enter Parliament and in some cases, they will decide the fate of entire parties.

Other electorates may act as a litmus test for the mood of the nation.

Here are some electorates to watch tonight.

Waiariki

Results from all the Māori electorates will be watched closely.

The very existence of MANA and the Māori Party in Parliament hinges on winning Māori electorate seats. Except for deputy leader Kelvin Davis, Labour's incumbent Māori-electorate candidates are not on its party list, so these votes will directly influence the make-up of Parliament.

Waiariki belongs to Māori Party co-leader Te Ururoa Flavell. He has been very focused on campaigning in the electorate this year, leaving most of the party's media duties to co-leader Marama Fox.

How the Waiariki electorate shapes up.
Photo credit: Newshub

That's because the Māori Party won't pass the party vote threshold, so needs to win at least one electorate seat to enter Parliament.

This is a little complicated. If the Māori Party win more seats through electorates than their percentage of their party vote entitles them to, Ms Fox won't return to Parliament, unless she can win in her own electorate.

If Te Ururoa doesn't win his seat but new candidate Howie Tamati takes Te Tai Hauāuru, Mr Tamati may find himself alone at the helm of the Māori Party, with neither co-leader returning to Parliament.

NB: You don't have to be on the Māori electoral roll to vote for the Māori Party.

Wellington Central

Several high-profile candidates are standing in Wellington Central. It's typically a Green party-vote stronghold, but the seat is usually won by Labour and the incumbent is finance spokesperson Grant Robertson.

He's likely to bring it home again, but the intrigue in this seat lies elsewhere, with Wellington Central looming as an indicator for how the Greens (represented by leader James Shaw) are tracking.

It will be interesting to watch whether Mr Peters holds onto that support this time round or whether it returns to National.

He has been campaigning hard in the area, but local farmers may fear he will prop up Labour and could switch their votes back to National.

How the Northland electorate shapes up.
Photo credit: Newshub.

Mr Peters has opposed Labour's tax on water, but it's a key policy for Labour.

Ilam

As a region that's seen rapid population changes following the earthquakes, Christchurch electorates may prove particularly volatile.

Ilam is currently held by the divisive Gerry Brownlee for National, but he faces stern opposition from independent candidate Raf Manji.

How the Ilam electorate shapes up.
Photo credit: Newshub.

Mr Brownlee has held the seat since 1996. He finished well clear in 2014, but a disgruntled consistuency and the option of a fresh face could loosen Mr Brownlee's grip.

Northcote

National's Dr Jonathan Coleman currently holds the Northcote electorate, but as the Minister of Health, he's represented the party in one of National's more contentious areas.

Are people frustrated enough about health to vote for the Labour candidate instead? Will his majority take a hit?

Action Station has erected billboards in the electorate, targeting Mr Coleman's record on mental health.

How the Northcote electorate shapes up.
Photo credit: Newshub.

Very few electorate seats directly affect the number of seats a party has in Parliament and this one is no exception. At number eight on the party list, Dr Coleman will make it back into Parliament, even if he loses his seat.